The present invention relates to an administering device and in particular to an automatic self-injecting device for administering a predetermined dose of a pharmaceutical substance.
Self-injecting devices for delivering pharmaceutical compounds are known, in particular for use by diabetics to inject insulin. Such known devices tend to be complicated to load, unwieldy and noisy to use, and require very precise handling. However, since diabetics need to self-inject on a very regular basis, they learn to use the devices in time and become used to the disadvantages.
In one such known device, a pre-filled conventional syringe is loaded into a cylindrical delivery chamber and a piston is retracted against the force of a spring and then locked in position. To administer the insulin the device is placed against the skin, the spring is released by the depression of a button and the syringe is pushed by the piston into the skin, which piston then compresses the plunger of the syringe to inject the insulin. The syringe is thrown away after use and an unused syringe is loaded when a further injection is required.
Devices such as that described above are shown in EP 0338806 (Owen Mumford Ltd), W088/08725 (Haselmeier), DE 3960926 (Dietronic) and DD 262585 (Tech Hoch, Merseburg), for example.
In another version of self-injecting device manufactured by Owen Mumford Ltd (not described in any patent literature known to the applicants) the release button is on the side of the device and is locked in position by a catch to prevent accidental actuation. The catch can be disengaged from the button by a sliding movement along the length of the device.
U.S. Pat. Nos. 4329988, 4226235, 3882863 and 3712301 (all in name of Survival Technology Inc.) concern devices for administering antidotes to be used by military personnel in the event of chemical warfare These automatic injectors are actuated by being pressed against the user's thigh. Premature actuation is prevented by means of a safety cap which has a central pin which prevents the piston being released